The aims of this project are: 1) to investigate the nature of the steroids in brain and 2) to reinvestigate the biochemical processes by which C-C bonds are cleaved. Of specific concern are those reactions by which C/27-sterols are converted into C/21-steroids (e.g., progesterone) and those by which C/21-steroids are converted into C/19-steroids (e.g., testosterone). The methods required for these studies include radioisotope technology using labeled steroids, in vitro incubations with various tissue preparations, isolation techniques involving various chromatographic procedures (TLC, partition chromatography, HPLC, etc) and spectrometric techniques, such as UV, IR and MS. 1) To study the first objective, we use modern chemical and spectroscopic techniques to characterize the various steroids and steroid conjugates that have reported to be present in brain tissues. Efforts will be made to determine whether pregnenolone or dehydroisoandrosterone are biosynthesized from sterols in brain tissue. When incubated with homogenates of rat brain, pregnenolone is metabolized to more polar compounds. We shall attempt to identify these metabolites since they may provide clues to the functions served by steroids in the brain. 2) We intend to reinvestigate the biochemical processes by which C/21-steroids (pregnenolone, progesterone) are converted into C/19-steroids (dehydroisoandro-sterone, androstenedione, testosterone). It is generally believed that hydroxylation at C-17 (of a C/21-steroid) must precede cleavage of the C-17, C-20 bond. We intend to study the possibility that hydroxylation at C-17 is not an obligatory step in the bioconversion of C/21-steroids to C/19-steroids.